This invention relates to a method for correcting the bidirectional printing alignment of a serial dot matrix printer.
A serial dot matrix printer prints on a medium by means of a print head that moves laterally and stops in a cyclical manner. Known causes of misalignment of the printed pattern in bidirectional printing (i.e., misalignment between positions of printing during lateral movement in one direction and during lateral movement in the other direction) include variations in the backlash of the gears in the drive mechanism, variations in the speed of motion of the carriage due to nonuniformity of parts (e.g., variation in rack pitch), and changes in the acceleration and deceleration time of the carriage motor (space motor) due to variations in the characteristics of circuit elements.
A system that has been adopted to correct such misalignment changes the read-only memory data with regard to the printing timing, as disclosed in Japanese Patent Application Laying-open No. 45070/1982.
A problem with the above system is that, since every printer has a different degree of misalignment, the alignment cannot be successfully corrected unless several types of read-only memories incorporating different correction amounts are provided.
Another problem is the difficulty of readjustment if the printing alignment is lost because of changes due to aging after the printer is in the possession of the user. The user cannot easily change the read-only memory data, nor is it customary for the user to keep a supply of read-only memories with different correction amounts written therein.